Lecture 18. Appropriate Cell Differentiation and Stem Cells Flashcards
What is important for appropriate cell differentiation ?
Time and space
How is the progressive nature of development reflected ?
Cells become more and more in their fate until eventually a single fate has become irreversibly determined
When is the fate of a cell determined ?
When it can no longer respond to changing environmental signals and change its differentiation pathway
What is specification ?
The first stage of commitment of cell fate. At this stage cell commitment is still capable of being reversed. The cell has received information but can still be further influenced by new information
What is determination ?
The information received by a cell has fixed its fate and will allow no further change
What can lateral inhibition generate ?
Spacing patterns
What is lateral inhibition ?
A means of ensuring that all cells in a field do not undergo the same differentiation pathway, at the same time
Give an example of a use of lateral inhibition ?
Used to space out the differentiation neurons in the developing nervous system
In embryos, what is lateral inhibition often the result of ?
Differentiating cells producing an inhibitory molecule that acts locally to prevent neighbouring cell differentiating the same way
How does lateral inhibition work in the delta-notch pathway ?
Spaces out the differentiation of neurons in the developing nervous system in time and space
What is the pathway that decides how the cell decides to become a neuron ?
Delta notch
How does a cell decide to become a neuron or not?
- Contiguous neural plate cells express neurogenin, delta and notch.
- With time, one cell expresses more delta into a neuroblast and inhibits the neighboring cells from following a neural fate
What technique have developmental biologists developed to be able to trace cells over time ?
Cell lineage analysis
What is cell lineage analysis needed for ?
Cell fate mapping
What is the concept of cell lineage analysis ?
A method to physically mark a cell early in development and observe it and its descendent cells at a later time
What has cell lineage tracing in the chick been used for ?
Used to map the migration pathway and fate of neural crest cells
Who pioneered cell lineage analysis ?
Nicole M. Le Douarin
What is the genetic tag used in cell lineage analysis ?
Green fluorescent protein
How is a genetic tag used in cell lineage analysis ?
Use of a transgene inserting the gene encoding the GFP protein into specific location of the DNA
Where does GFP come from ?
Jellyfish
What is a brainbow ?
Transgenes tracing individual cells and descendants in developing brain of transgenic mice
What is the purpose of mouse blastocyst being marked with unique colours ?
Follow them over time to demonstrate clonal origins of cells
What is the function of positional information ?
Creating a spatial pattern of cell differentiation
How could a pattern emerge in the embryo cells ?
By receiving a positional address through a set of molecular signals unique to that position
How do cells receive positional information ?
- Localisation of cytoplasmic determinants
- Induction
- Gradients of signals
- Role of physical environment
What is the function of localisation of cytoplasmic determinants ?
A mechanism to make cells different to each other
What is the basis of induction ?
Cell to cell signaling
What is a morphogen ?
A signal involved in pattern formation where cells have a graded response depending on the level of the signal they are exposed to